Pulverizer



Dec. 29, '1936, H. R. coLLjs.

PULVERIZER` Filed Nov. 4, 1931 4 Sheets-Sheet 1 Dec. 29, 1936. H. R. coLvLlNs PULVERIZER Filed Nov. 4, 1931 4 sheets-sheet 2 Dec. 29, 1936. I H. R; COLLINS 2,066,139

' PULVRIZER i Filed Nov. 4, 1931 4 sheets-sheet :s

Slm/cantor,

atroz new Dec. 29, 1936. H. R. COLLINS PULVERIZER Filed Nov. k4, 1931 v 4 Sheets-Sheet 4 HARRYR/mo/va COLL/N5 Patented Dec. 29, 1936 UNITED STATES PATENT OFFICE PULVERIZER Harry Raymond Collins, Allentown, Pa., assgnor to The Babcock & Wilcox Company, Bayonne, N.v J.; a corporation of New Jersey Application November 4, 1931, serial No. 573,021

24 claims. (ci. 83-45) This invention aims to provide an improved -casting is a housing, member I6 having a cengrinding or pulverizing machine of the type tral hub-like extension I1 on its lower side proshown in my Patent No. 1,386,093 dated August viding journal bearing for a shaft stepped up- 2, 1921, wherein a series of crushing balls are reright therein. Supported vertically therewithin volved about a central axis upon an annular is a rotary main shaft I8 having intermediate raceway. or opposite end journalment in bearing I9 pro- Several objects and advantages are contemvided centrally of the aforesaid casting as by plated, and these as likewise the invention itself separate casting bolted thereto as shown. These will be best understood by description with refbearings of course have liners or bushings 20 erence to the attached drawings illustrating one adapted to lubrication as common to machine 10 practicable embodiment, along with several modshaft assemblies.

ications which may be more adaptable to dif- Said shaft is adjustably stepped in thisinferent working conditions. stance upon a pintle Abearing 2| having a wearing In said drawings: disk 22 thereunder with bottom-washer 23 restl Fig. 1 is a side view of the illustrative embod1- ing against a screw 24, the latter being turnable 15 ment, showing one-half in vertical section and in adjusting nut 25 carried by a cap l2li which the other half in elevation; y is fastened to said extension of the housing and Fig. 2 is a plan view of the same showing onein turn houses these parts as a step support. half open with upper parts removed and the Said screw shown projecting from this `cap is other half closed; squared for locking to adjusted position by'nut 20 Fig. 3 is a plan view of the material feed mech- 21,' While packing to prevent escape of bearing anism shown sectionally in Fig. 1; lubricant may be held by a gland nut 28 bolted Fig. 4 is a section on theline 4-4 of Fig. 1; with the former to the cap end. Fig. 5 is an end view on the sectional line 5-5 The aforesaid shaft carries a. pentagonal drivof Fig. 1; ing head 29 on its upper end, secured thereto as 25 Fig. 6 is a partial sectional viewv of a modiby key-Splining and lock-nut fastening; Its cation embodying a single series of grinding dlVe means by Which high Speed lOtatiOn may balls; be imparted will be later described.

Fig. 7 is a similar view of another modification Supported on the upper end of the aforemenhaving three series of balls; tioned casting (I2) is a grinding ring 30 of an- 30 Fig. 8 is a like view of a. further modification nular form having an annular grOOVe fitting having four series of balls; and over a corresponding ridge 3l of said casting Fig. 9 is a fragmentary view diagrammatically for accurate centering thereon. These two representing the chilling of the ball-raceway Darts are rigidly Connected together aS by bolts surfaces. 32 passed through the ring. This ring is shown 35 The exemplary machine or mill being essenformed with oppositely inclined faces 33'and 34 tially circular in form is mounted advantageousat opposite sides of its inner periphery, having 1y on a circular concrete foundation I0 having raised (see Fig. 9) and chill-hardened surfaces of a ring-.plate II grouted in its top to assure a glassy smoothness-and hardness represented by rm, even and level rest. cross-hatched portions thereof providing annu- 40 Its base or' body part is provided in this inlar ball-raceways. Being subjected to heavy stance by an annular bowl-like casting I2 faswear and pressures, the ring is preferably cast tened down upon said plate by bolts (not shown) froma mixture of iron having a low content of anchored in the foundation. This casting is sulphur, silicon and phosphorus to avoid weak- 4, formed with a radial clean-out opening at one ening, with manganese from 0.4 to 0.6 percent 45 side closely normally by a door I3, aording to give depth to the chilled faces, followed by ready means of removing such foreign material mottled iron and in turn followed bygray iron or matter as may nd its way into the machine, to give strength. The depth of the chilling over while a skeleton sliding plug I4 serves to prean arcuate area in straight and angular lines to vent accumulation of pulverized material setthe chill as represented in aforesaid Fig. 9 is such 50 tling in said clean-out opening. At the opposite as to present a substantially wide and hard surside, an opening I5 adapted to connection with face, susceptible of grinding to a smooth, true a conduit is provided for a purpose which will annulus for the balls so as to minimize ball later appear. jumping, vibration, noise and wear. vSecured as by bolting to the underside of said Between the raceway surfaces of said ring, an 55 inner peripheral extension is provided as by plate 36 machined or otherwise flxed thereto and desirably having a marginal bead around its upperl edge. This extension serves as a shelf for sup- 5 porting the balls when assembling the mill, and as a drop-ledge for material during operation of the mill. v

On the upper (3l) of the raceway surfaces, an Vannular series of balls 36 is revoluble. These balls are of forged steel, heat-treated and hardened. In this instance there are ten of twelveinch diameter to the series, weighing approximately 256 pounds each. Balls of such size and weight will nip and crunch quite large granular or lumpy material without the snghtest dimoul- On the lower (34) of said raceway surfaces is .'revolublel another annular series of balls 61 the same as the former except as to size and number, there being in this instance twelve of only ten-inch diameter -to the series, weighing approximately 1-i8v pounds each. 'I'hese of` course wrk on ilner material and crush to the pulverizing point. Y

The upper series of balls is held down on the upper raceway of the grinding ring by a pressure plate or disk 66 having two faces 39 at obtuse angular relation of approximately 1 20 degrees apart, or with one at 15 degrees from the horizontal and the other at l5 degrees from the vertical, providing annular bearing raceways of different diameters concentric with and opposite to said raceway of the ring. These faces have-raised and chill-hardened surfaces represented by the crosshatched portions thereof, similar to and for the same purpose as the raceways of said ring. The plate or disk 'is also cast preferably from the same metal as thek grinding ring to assure like strength,

. hardness and wear qualities. It rests upon the 40 balls with its said surfaces contacting their upper sides equi-distant from a dlametrical plane perpendicular to the raceway of the ring and so h olds them in a three-point balanceas illustrat- -ed inFig. 1 by the dotted lines through the balls.

In this position it engages centrally over or with the driving head (26) on the rotary shaft so as to be driven therewith. It is adapted to yielding pressure action on the balls, in this instance by an annular series of bolts 4X6 compressing springs 6I thereagainst within wells 62 therein formed ffor the purpose.

The lower series of balls is held up on the lower raceway of the grinding ring by another pressure plate or disk 63, having faces M corresponding to-those of the first, and of the same material of which it is formed. This latter plate bears under the balls with its said surfaces contacting their lower sides equidistantly from a diametrical plane perpendicular to the raceway of the 00 ring in the same way as theformer and similarly engages over or with the driving head on the rotary shaft for driving therewith. This plate is likewise adapted to yielding pressure-action on.

the balls, in this instance by passing the afore- 35 mentioned bolts 66 therethroughso that the two x plates will be drawn `together and serve at the sa time to support the lower one.

e two plates thus drawn togethertend toA the upper series of balls of course being revolved `a lesser number of times per cycle than the lower ameter and the lower series travels an annulus of 5 34.5 .inch diameter andthe machine is driven at the rate of 100 revolutions per minute, the balls of the upper series (having a total weight of approximately 2,560 pounds) will be revolved 266 times per minute, while the balls of the'lower l0 series (having a total weight of approximately 1776 pounds) will be revolved 345 times per mlnute.

In this illustrative machine, the rotary shaft is driven by a ring-gear 66 carried by spider 66 15 keyed and locked thereon within the aforementioned housing (I6). This gear meshes with pinion 61 keyed on the end of a drive shaft 66 projected horizontally into said housing.

The lastenamed shaft is shown extending 20 through a combined oil-pump and reservoir casing 66 connected to an open side of the housing formed with bottom slopage tleretoward for drain into its lower reservoir space through communieating passage 60. Said shaft has support in 25 bearings 6| and 62, the former being advantageously formed as part of said casing and the latter being xed on a standard IIIx formed desirably as part of the concrete foundation.

Eachof these bearings of course has the usual so liners or bushings 6I with channels for lubrication. 0n its other end the shaft carries a pulley or head 66 for either belt or `flexible-joint connection with a power-drive plant (not shown).

It also'carries a .pulley 66 for` driving-belt con- 35 neetion with another party later described. A

-grooved pulley 66 thereonl adjacent the casing provides for belt drive of the oil-pump next described.

Said oil pump .in this instance comprises a o pair of pumping gears 61 and 66 (see Fig. 5) housed in the wall of the aforementioned casing v(49) at thelevel of its reservoir space and .driven by grooved pulley 66 from the first-mentioned such pulley on the driving shaft. These 45 pump gears may be exposed to the oil in the reservoir space of the casing, or draw it in by siphonic action through a lead-in pipe 61|,QasA preferred. An outlet pipe. 6l therefroml leads through a flow-gauge 62 to adistributing mani- 50 fold '63. From this manifold, a pipe 66 leads to the lower and step-bearings of the rotary shaft"(l6), another pipe. 66 leads 'to the drlvfing shaft bearing (6I), a third pipe 66 leads tothe teeth of the driving-pinion (61) and a 55 fourth pipel 61 leads to the upper bearing (I6) of the rotary shaft. A l

'I'he pumped oil excess or overilow from the aforesaid parts-returns to the reservoir space of vthe casing, which is provided with a filler cap so 66 for replenishing the supply as necessary, while a valve controlled drain 66 in the bottom of ythe casing provides for drawing oi! used oil and sediment. A thrust-collar 16 therewithin on the driving shaft is advantageously splattered with 65 sumcient lubricant by an oil-slinger blade 1I t thereon dipping into the supply. The described grinding elements are encased as by a cylindrical shell 12 shown resting on top of the grinding ring ()v and having a retainer 70- ring 'I3 bolted thereto with rib-tting into a centering groove thereof similarly tothe latter's mounting on the base casting. This shell has a tapering top'16 connecting with a Aflue-pipe (not shown) leadingto a collecting or storage u` tral opening. Around this neck are a series of deilectors 15 arranged in tangential relation thereto (see Figs. l and 4). suspending from around the lower ends of these bailles is an inverted cone-funnel 11 opening above the upper pressure-plate (38). Encircling the lower end of this funnel and also said plate is an inner shell-member 18 secured on the grinding ring concentrically with the outer shell member and providing a trough-space -around the grinding elements within -the main shell area, as also an annular passage 19 therebehind. On top of said upper pressure-plate, a cover plate 80 having a raised conical center under the funnel and thimbles 8| around the compressor y springs shield the saine againstmaterial dropped through the funnel and allow it to be thrown oi against the trough sides. A door 83 in one sideof the main sheil provides access thereinto for cleaning and inspection purposes.

Encircling the lower pressure-plate (43) is another inner shell 84 secured tov the bottom of the grinding ring and providing an annular passage 85 therebehind as also a discharge opening 86 below the lower ball level. This inner shell together with the lower pressure-plate in effect forms the bottom of the trough, `of which the aforesaid grinding ring forms part of the side.

The' aforesaid annular passages 19 and 85 behind the trough wall are opened to each other in this instance by an annular series of communicating passages 30 through the grinding ring behind its raceway surfaces. with the effect of a continuous annular space between the trough and outer shell from the bottom of the machine to above the lower end of the funnel.

A continuous air blast through these passages from the bottom toward the top of the machine is maintained during operation of the machine. This air blast is generated by a fan unit 81 having outlet conduit 88 connecting with the aforef said opening 5 of the casting. member (1 2). This fan unit is preferably driven independently.

The material to be .-pulverized in the machin-e is fed through a hopper 89 having spout 90 extending Linto the inner trough space with a. swinging baille-plate 9| on its end. The mate' rial is supplied'through a conduit (not shown) connecting with the top ofthe hopper. It drops onto an arcuate plate 92 over the edges of which it ris pushed by a swinging blade 93 in regulated feed. This blade oscillates on shaft rocked by lever 95 connected by pitman 96 to'a crank on the end of a shaft 91. `Said pitman is adjustable on the lever to vary the stroke of oscillation according to the rate of feed desired. The last-named shaft is rotated by small ringgear 98 driven by pinion 99 on another shaft |00, while the latter is driven by pulley |0| on its end over which a belt `from the aforementionedy pulley 55 on the driving shaft is trained.

The operation of the machinewill be obvious to those skilled in the art, but a brief description" thereof will facilitate understanding and render it entirely clear. Let it be assumed that .the material is feeding through the hopper (89) and ground under the upper ball series, it sifts down onto and over the extension plate 35 from which it trickles onto the lower series -of balls by which it is similarly crushed to a finer degree. Passing from under or around the lower ball series, the ground material drops through the opening (86) into the space beneath.. As it thus drops, it is caught by the air blast and carried upwardly behind theV trough space through the communicating. passages 85, 30 and 19 toward the top of the machine. An eddy of air more or less compressed within these passages forms in the open space above the shell member 18 so that any very coarse particles unsuspended therein will strike against the funnel 11 and drop back into the trough for regrinding. The other particles however will be carried upwardly against the defiector plates 16 and around the neck 15, with the very ne pulverized particles carrying off with the blasted air `through the flue-pipe and the coarser particles dropping into the funnel so as to return for further grinding like the very coarse particles pjhead in place of said plate. An apron |04 serves -to deflect the ground material discharged into the bottom air blast space. Otherwise, the construction and assembly is essentially the same.

In the modification of Fig. 7 wherein there are three ball series |02, 36'and 31, a combination of the forms of Figs. 1 and 6 may be employed.

In this case there are tvvogrinding rings with separators` between, one having a single raceway as in Fig. 6 and the other having double raceways as in Fig. 1. The bolts 40 are then advantageously extended through an extra upper pressure plate (38) and carry two sets of compressor springs (4|)working lon these plates. Two extension plates 35 also are'required, but otherwise the assembly is the same as described with reference `to Fig. 1.

In the modification of Fig. 8', wherein four series of balls are used, the structure is in effect a mere duplication of that shown in Fig. 1. In this case the bolts 00 are extended through double upper and double lower pressure plates and have two sets of compressor springs working on the upper ones.

These modified constructions may be desirable .for different vinstallments where varying degrees of pulveriz'ation are desired, the crush and grindy being of course ner with an increased number of ball series. In al1 essential'respects however, the form' and mode of operation are the same as described with reference to the main embodiment.

The advantages and desirable improvement face on which the' balls revolve, an annular plate lis having a plurality of inclined surfaces at obtuse angular relation bearing upon the balls so as to hold them on the inclined face of the ring plate and revolving the balls when itself rotated, means for rotating the second-named plate, and means holdingthe same with yielding pressure against the balls.

2. In a pulverizing machine, an annular series of crushing balls, a ring plate having an inclined surface on which the balls are revolved, a concentric plate having double inclined faces at obtuse angular relation in two-point bearing upon the balls opposite said surface of the ring plate for centering and holding the same thereon, means holding the concentric plate in yielding pressure against the balls, and means rotating said concentric plate to frictionally revolve the balls in grinding motion.

3. In a pulverizing machine embodying a' plurality of annular series of grinding balls, a grinding plate having a plurality of annular raceways on which the ball series rotate, means holding the ball series under yielding pressure on their respective raceways. means feeding the material to be ground over the bali raceways and a discharge for material ground on the raceways: said grinding` plate having an annular series of passages therethrough behind the raceways, means providing a space below the discharge communicating with said passages and into which the discharge opens, means providing a space behind the feeding means also communicating with said passages, and means generating a continuous air blast from the first to the second named space through said passages for carrying oiI the ground material.

4. In a pulverizing machine, a plurality of annular series of grinding balls'at diierent levels, a grinding plate having annular raceways on which' the ball series revolve and a series of passages therethrough behind saidv surfaces, means holding the ball series to their respective raceways under yielding pressure, means for rotating the balls, means feeding the material over the ball raceway surfaces for grinding under the balls, a gravity discharge for ground material,` means providing a space under said discharge communicating with the passages in said grindingplate, means` providing a space above the feeding means and also communicating with said passages ofthe grinding plate, means generating a blast of air to convey 'the discharge from the ilrst to the second of said spaces through said plate passages, and means for returning the coarser particles of ground Vmaterial to feed under the balls while allowing the nner particles ,to pass off toa point of collection.

.5. A pulverizing machine comprising in .com-

" binatlon, an annular series of grinding balls, a

grinding ringhaving a raceway surface on which the balls revolve and passages outside of said raceway surface, a concentric plate holdingthe balls on their raceway surface under yielding Pressure and revolving the same when itself rotated,v means rotating said plate, means ,feeding thematerial to be ground under the balls, a' ara-vitydisclrarge for the ground material below the balls, means providing a space into which said discharge opens, means providing another space communicating with the first-named space through passages in the grinding ring behind the feeding means, means generating a continugrinding ring intermediate said series, upper and yieldably press said grinding balls against saidv non-rotary ring, means for supplying material to said rows oi' balls in series, and means to cause air to remove the ground material from said mill and return coarse particles from the air to be. again ground in said mill.

8. A pulverizing mill comprising a' grinding ring having an inclined ball-contacting surface, a circular row of grinding balls each having a single point contact with said ring, a second grinding ring having a pair of relatively angularly arranged inclined ball-contacting surfaces each having a single point contact with each of said balls for holding said balls in position between said rings. and means for frictionally moving said balls relative to said rings through one of said rings.

9. A pulverizing mill comprising a non-rotary grinding ring having an inclined ball-contacting surface, a circular row of grinding balls each having a single point contact with said non-rotary ring, a rotary grinding ring having a pair of relatively angularly arranged inclined ball-contacting surfaces each having a single point contact with each of said balls for holding said balls in position between said rings, and means for frictionally moving said balls relative to said rings v through said rotary ring.

10. A pulverizing mill comprising a mill casing enclosing a plurality of vertically spaced horimntally arranged rotary grinding rings, a horizontally arranged non-rotary grinding ring intermediate said rotary rings, a circular row of rolling grinding elements contacting with and positioned between each of said rotary rings and saidlintermediate ring, means for rotating said rotary rings. means for feeding material to be pulverized directly to the outer side of the uppermost row of grinding elements and directing the .material pulveriud by said uppermost row of grinding elements to the inner side of the lowermost row of `grinding elements, and means for removing pulverized material Ileaving the outer side of said .lowermost row of grinding elements.

11.. A pulverizing mill comprising a mill casing enclosing a plurality of vertically spaced horizontally arranged rotary grinding rings, ahoriu zontally arranged non-rotary grinding ring intermediate said rotary rings, a. circular row of rolling grinding elements contacting with and positioned between each of said rotary rings and said intermediate ring, means for rotating said rotary rings, means for feeding material to be pulverized directly to the outer side of the uppermost row of grinding elements and directing the material pulverized by said uppermost row of grinding elements to the inner side of the lowermost row of grinding elements, and an air blast for sweeping up pulverized material leaving the outer side of said lowermostrowof grlndingelements.

y 12. A pulverizing mill comprisinga'niill casing having a material outlet in'th 'pperyp and enclosing a plurality. o horizontally arranged lrotary grindin'g horizontally arranged non-rotary grind intermediate said rotary rings, acircula rolling grinding elements contacting with antipositioned between each of said rotary rings and said intermediate ring, means for rotating said rotary rings, means for feeding material to be pulverized directly to the outer side of the uppermost row of grinding elements and directing the material pulverized by said uppermost row of grinding elements to the inner Aside of the lowermost row of grinding elements, and means for directing a stream of air past the outer side of said lowermost row of grinding elements to sweep up pulverized material leaving said row and directing .the material-laden air outside said rows of grinding elements to the upper part of said mill casing.

13. A pulverizing mill comprising a mill casing enclosing a plurality of spaced grinding rings, a circular row of rolling grinding elements contacting with and positioned between said rings, means 4for rotating one of said rings, means for feeding material to be pulverized to one side of said row `of grinding elements, and downwardly projecting baiiie means arranged to restrict the discharge from the opposite side of said row of grinding elements and direct pulverized material leaving said row of grinding elements into the path of an air stream adjacent thereto.

14. A pulverizing mill comprising a mill casing enclosing a plurality of spaced grinding rings, a circularI row of rolling grinding elementslcontacting with and positioned between said rings, means for rotating one of said rings, means for feeding material to be pulverized to the outer side of said row of grinding elements, and an linclined baille depending from one of said grinding rings and at the inner side of said row of grinding elements for directing pulverizedmaterial leaving said row of grinding elements outwardly into the path of an air stream adjacent thereto.

l5. A pulverizing mill comprising a mill casing enclosing a plurality of vertically spaced horizontally arranged rotary grinding rings, ar

horizontally arranged non-rotary grinding ring intermediate sa-id rotary rings, a circular row of rolling grinding elements contacting with and positioned between each of said rotary rings and said intermediate ring, means for rotating said rotary, rings, means for feeding material to beA the outer side of said lowermost row of grinding elements.

16. A pulverizing mill comprising a mill casing enclosing a plurality of vertically spaced horizontally arranged rotary grinding rings, a horizontally arrangednon-rotary grinding ring intermediate said rotary rings, a circular row of rolling grinding elements contacting with and ,positioned between each of said rotary rings and said intermediate ring, means for rotating said rotary rings, means for feeding material to be pulverized to the outer side of the uppermost row of grinding elements and directing the material pulverized by said uppermost row of grinding ,elements to thefinner side ofthe lowermost row of grinding, elements, baiile means for restricting he iiow ofjmxaterial between saidrows, means for lowermost11,0W ofv grinding elements, and bailie means for' restricting the pulverized material discharge from said lowermost row of grindingy elements.

17. A pulverizing mill comprising a mill casing enclosing upper and lower rotary. grinding. rings, a non-rotary intermediate grinding ring, an upper circular row of rolling grinding elements contacting with and positioned between said upper and intermediate rings, a lower circular row of rolling grinding elements contacting with and positioned between said intermediate and lower material leaving the outer side of said lower row of grinding elements.

18. A two-stage pulverizer mill comprising a mill casing enclosing a horizontally arranged rotary top grinding ring,` a horizontally 'ar--v ranged non-rotary intermediate grinding ring, a horizontally arranged rotary bottom grinding ring, an upper circular row of grinding ,balls positioned between and contacting with said top and intermediate rings, a lower circular row of assing an airstream past and sweeping up pu'l` @verized materialfjleaving the outerside of said' grinding balls positioned betweenandcontacting with said intermediate and bottom rings, resilient means for holding said top and bottom rings in yielding relation with said upper and lower rowsv of balls respectively and supporting said bottom ring, means for rotating said top and bottom rings relative to said intermediate ring, means vfor directing material to be pulverized to the outer side of said upper row of balls, and saidl top and bottom rings being constructed and arranged relative to said intermediate ring and mill casing to cause the material being pulverized to pass inwardly through said upper row of ballsy mill vcomprising a mill casing enclosing a horizontally arranged 1 rotary top grinding ring, a horizontally `ar ranged non-rotary intermediate grinding ring, a horizontally arranged rotary bottom' grinding ring, an upper circular row of grinding balls ring including a series of bolts extending through said top and bottom rings and compression springs held by said bolts against one of said last mentioned rings, means for rotating said top and bottom ring relative to said intermediate 10 fring, means for directing material to be pulverized to the outer side of said upper row of balls, and said top and bottom rings being constructed and arranged relative to said intermediate ring and mill c'asing to cause the material being pulverized to pass inwardly'through said upper row 'of balls and then outwardly through sa'id lower row of balls.

20. A two-stage pulverizer mill comprising a mill casing enclosing a horizontally arranged rotary top grinding ring, a horizontally arranged non-rotary intermediate grindingring, a horizntally arranged rotary bottom grinding ring, a upper circular row of grinding balls positioned between and contacting with -said top 2.5 and intermediate rings',`a lower circular row of grinding balls positioned between and contacting with said intermediate and bottom rings, said upper and lower rows of balls being concentric and the balls of said lower row being of smaller diameter than the balls of said upper row, means for holding said top and bottom rings in yieldving relation with said upper and lower rows of balls respectively and supporting said bottom ring-including a series of bolts extending through said top ,and `bottom rings and compression springs held by said bolts against one of said last mentioned rings, means at the opposite side of said top and bottom rings from said compression springs for rotating said top and bottom rings 40 relative to said intermediate ring, means for directing material to be pulverized to the outer side of said-upper row of balls, and said top and bottom rings being constructed and arranged relative to said intermediate ring and mill casing to cause the material being pulverized to pass inwardly through said upper row otballs and then outwardly through said lower row of balls.

l. A multi-stage pulverizer mill comprising upper and lower rotary' grinding rings, a non- .50 rotary grinding ring adjacent said upper and lower rings, an upper circular row of rolling grinding elements positioned between and contactingswith said upper and non-rotary rings, a lower circular row of rolling grinding elements lili positioned between and contacting with said nonrotary and lower rings, and resilient means interconnecting and rotatable'with saidupper and lower rings and arranged to exert a downward resilient pressure on said upper ring and upper o0 row of Grinding elements and an upward resilient .pressure .on-said lower .ring andv lower row of grinding elements.

22. A multi-stage pulveriaer mill comprising upper and lower horizontally arranged rotary grinding rings, a' horizontally arranged non-` 5 rotary grinding ring intermediate said upper and lower rings, an uppercircular row of.rolling grinding elements positioned between and contacting with ,said upper and intermediate rings.

.a lower circular row of rolling grinding elements 1| positioned between and contacting with said intermediate and lower rings, and resilient means interconnecting and rotatable with said upper and lower rings and arranged to exert a downward resilient pressure on said upper ring and l: upper row of grinding. elements and an upward resilient pressure on said lo'wer ring and lower row of grinding elements.

23.-A 'multi-stage pulverizer mill comprising upper and lower horizontally arranged rotary 2* grinding rings, a horizontally arranged stationary grinding ring intermediate said upper and lower rings, an upper circular row of grindingballs positioned between and contacting with said upper and intermediate rings', a lower circular row 2 of grinding ballsi positioned between and contacting withsaid intermediate .and lower rings, and resilient means interconnecting and rotatable with said upper and lower rings and arranged to exert a downward resilient pressure on 3 said upper ring and upper row of balls and an upward resilient pressure on said lower ring and lower row of balls and to rotatably support said lower ringv and lowery row of balls from rsaid intermediate ring.

y24. In a planetary"ball mil1,.a closed housing, a vertical shaft rotatably mounted therein, means l for rotating said shaft, grinding elements com- Y prising two separate series of balls adapted to travel in two superposed-vhorizontally disposed 4 annular paths, ,a plurality of grinding rings centered about the shaft between which said balls. are conined, said rings including an outer grindfv ing ring fixed within said housing and having two grinding surfaces, one for each series of .i balls, an upper inner. ring arranged to contact with the inner upper surfaces of the upper series of balls, a lower inner ring arranged to contact with the inner lower surfaces of the lower series of balls, means for connecting the upper and i lower inner rings for simultaneous rotation and for yieldably urging the upper and lower inner rings toward one another, and connecting means for rotatingsaid inner ringsrelative to said xed ring, said connecting means including relatively movable parts whereby the inner rings are permitted limited vertical movement with relation t0 said shaft.

HARRY RAYMOND S. 

